Fluid-blast circuit interrupter with straight-line driving mechanism



Oct. 26, 1965 B. P. BAKER ETAL 3,214,541

' FLUID BLAST CIRCUIT INTERRUPTER WITH STRAIGHT-LINE DRIVING MECHANISM 3 Sheets-Sheet 1 Filed April 3. 1961 Oct. 26, 1965 B. P. BAKER ETAL 3,214,541

FLUID BLAST CIRCUIT INTERRUP'I'ER WITH STRAIGHT-LINE DRIVING MECHANISM Filed April 5, 1961 3 Sheets-Sheet 2 OOi %K\ h MW I 65 I h- Oct. 26, 1965 B. P. BAKER ETAL 3,214,541

FLUID BLAST CIRCUIT INTERRUPTER WITH STRAIGHT-LINE DRIVING MECHANISM Filed April 5, 1961 3 Sheets-Sheet 3 Fig. 4

United States Patent 3,214,541 FLUID-BLAST CIRCUIT INTERRUPTER WITH STRAIGHT-LINE DRIVING MECHANISM Benjamin P. Baker, deceased, late of'Monroeville, Pa., by

Mellon National Bank and Trust Company, executor,

and Charles F. Cromer, Penn Township, Westmoreland County, and Wayne S. Aspey, Monroeville, Pa., as-

signors' to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 3, 1961, Ser. No. 101,620 4 Claims. (Cl. 200-445) This invention relates to circuit interrupters in general and, more particularly, to circuit interrupters of the fluidblast type. I

A general object of the present invention is to provide an improved fluid-blast circuit interrupter of simplified construction and highly efficient in operation.

A more specific object of the present invention is the provision of an improved circuit-interrupting structure including a confined housing having disposed therewithin a pressure-resistant interrupter tube. Preferably, a pair of simultaneously-movable U-shaped contact structures are moved externally of the interrupter tube and into the interior \of the interrupter tube during the opening operation.

A further object of the present invention is the provision of an improved live-tank type of circuit interrupter supported up in the air by suitable insulating means of length commensurate with the voltage rating of the device, and to associate an improved interrupting structure with the live-tank circuit interrupter preferably having in conjunction therewith an improved operating mechanism. I Another object of the present invention is the provision. of an improved circuit interrupter of the type having an interrupter tube disposed interiorly within a surrounding pressurized housing, in which the interrupter tube is formed of highly-pressure resistant metallic material for withstanding the high pressure.

Still another object of the present invention is the provision of a circuit interrupter of the type set forth in the immediately preceding paragraph having associated therewith a pair of movable U-shaped contact structures, each contact structure having a movable pressure-generating contact and .a movable interrupting contact.

Another object of the invention is to provide an improved operating linkage for simultaneously establishing a pair of pressure-generating arcs and a serially-related pair of interrupting arcs.

Further objects and advantages will readily become apparentupon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 is a side elevational view of a three-phase high-voltage fluid-blast circuit interrupter embodying features of the present invention, with the contact structure being illustrated in the closed-circuit position;

FIG. 2 is an end elevational view of one of the three I pole-units of the circuit interrupter of FIG. 1;

FIG. 3 is a longitudinal vertical sectional view taken through one ofthe live-tank interrupting structures of the circuit interrupter of FIGS. 1 and 2, with the contact structure being illustrated in the closed-circuit position; and,

FIG. 4 is a view somewhat similar to that of FIG. 3, but illustrating a modified type of arc-extinguishing assemblage, with the contact structure being illustrated in the fully open-circuit position.

Referring to the drawings, and more particularly to FIGS. 1 and 2 thereof, there is illustrated a three-phase circuit-interrupting assemblage, generally designated by the reference numeral 1. The three pole-units are respectively designated by the reference letters A, B and C. As

ice

shown in FIG. 1, the three'pole-units A, B, and C are mounted upon an angle-iron framework 2. The framework 2 is at ground potential and is supported upon a concrete base 3. Situated at the right-hand end of the framework 2, as viewed in FIG. 1, is an operating mechanism housing 4. Any suitable operating mechanism may be employed with the present invention, such as solenoid mechanism, pneumatic mechanism, or a hydraulic mechanism. The particular mechanism device 5, disposed within the mechanism housing 4, constitutes no part of the present invention; and any conventional type may readily be employed.

As viewed in FIG. 2, it will be noted that a reciprocally-operable operating rod 6 extends upwardly through a housing tube 7, and is pivotally connected to one end of a bell-crank lever 8. The crank-arm 8 is keyed to an operating shaft 9, extending in opposite direction from the crank-arm 8, as viewed in FIG. 2 of the drawings.

The rotatable operating shaft 9 is keyed to a pair of crank-arms 10, which, in turn effect reciprocal horizontal movement of a pair of longitudinally-extending operating rods 11, which extend below the insulating columns 12 supporting the elemental circuit-interrupting units, or building-block units 13.

The horizontal reciprocally-movable operating rods 11 are pivotally connected to bell-cranks 14, which are pivotally mounted on shafts 15. The bell-cranks 14 have arms 16, which have pivotally connected thereto, at their free ends, insulating operating rods 17, which extend vertically upwardly interiorly within the porcelain supporting columns 12.

The upper ends of the insulating operating rods 17 are employed to effect the opening and closing movement of the movable contact structure associated with each of the circuitinterrupting units 13, as more fully described hereinafter.

With reference to FIG. 2 of the drawings, it will be observed that extending angularly downwardly into each of the pressurized housing structures 18, associated with each interrupting unit 13, is a pair of terminal bushings 19, 20, having terminals 21, 22, respectively, at their outer extremities. Depending upon the voltage requirements, one of the interrupting units 13 may be employed, or, as illustrated in FIG. 2, a plurality of such units 13 may be arranged in series being connected by a conductor 23. Using only two such units 13, it will be apparent that the electrical circuit passing through the pole-unit C includes the line connection L outer terminal 21, through the ter* minal bushing 19, int-o the unit 13, out of the unit 13 through terminal bushing 20 to external terminal 22 thereof, connector 23, and in similar fashion through the righthand arc-extinguishing unit 13 of FIG. 2 to the righthand line connection L With reference to FIG. 2, it will be observed that secured, as by welding, to the upper side 24 of the pressurized metallic tank 18 is a cylindrical support member 25, having an outer support-flange portion 26, which serves to fixedly support in proper operative position the support flange 27, associated with each of the terminal bushings 19, 20. As well known by those skilled in the art, each terminal bushing 19, 20 has an externally-located weather-proof casing 28 and an internally-disposed weather-proof casing 29 (FIG. 4). A terminal stud 30 (FIG. 3) extends centrally through each of the terminal bushings 19, 20, and has threadedly secured and clamped thereto, adjacent the lower end thereof relatively fixed contact adapters 31. The contact adapters 31 provide contact housings for relatively stationary contact structures, generally designated by the reference numeral 32.

With reference to FIG. 3 of the drawings, it will be noted that the relatively stationary contact structure 32 comprises a plurality of circumferentially positioned contact finger segments 33, which make contacting engagement with a pair of movable interrupting contacts 34. Disposed interiorly within each contact finger cluster 32 is a movable tubular arcing contact 35, which has limited downward fol-lowing movement with respect to the movable interrupting contact 34, as limited by a flange portion 36 engaging a shoulder 37 associated with the finger contacts 33.

During the opening operation, as illustrated more clearly in FIG. 4, the tubular arcing contacts 35 move downwardly into following relation with respect to the movable interrupting contacts 34, as biased by compression springs 38, so that interrupting arcs 39 (FIG. 4) are terminated at the arcing contacts 35, and not at the lower ends of the finger contacts 33. As a result, the finger contacts 33 are maintained in good condition for good contact-carrying function in the closed-circuit position of the interrupter, as illustrated in FIG. 3 of the drawings.

Each pressurized metallic interrupter housing 18 has disposed therein aninsulating interrupting tube 40, maintained in a fixed operative position by means of positioning plugs 41 fixedly secured to the end cover plates 42, 43 of the tank structure 18. Suitable bolts 44 are provided to maintain the cover plate 43 in a proper position.

The right-hand positioning plug 41 has associated therewith a check valve 45, which closes during the existence of high-pressure conditions within the pressure-generating chamber 46 provided interiorly within the interrupting tube 40. Upon a subsidence of the pressure within the pressure-generating chamber 46, the check valve 45 will reopen, as biased opened by a spring 47, to enable fluid to pass into the tube 40 from the region 48 within the outer pressurized metallic casing 18.

As shown in FIG. 3, the two movable interrupting contacts 34 are secured to a reciprocally-operable cross-head structure, generally designated by the refernce numeral 49. Generally, the cross-head structure 49 includes an upper spaced pair of insulating bars 50, secured by bolts 51 to fixedly clamp thereby the lower ends of the two interrupting contacts 34, and also the lower ends of two movable pressure-generating contacts 52. The two insulating bars 50 have brackets 53 associated therewith at the outer extremities and centrally thereof, which are secured to a metallic channel-shaped member 54, providing a pair of race-ways 55. Disposed within the race-ways 55 are a pair of driving rollers 56, secured to the outer free ends of a pair of rotatable driving cranks 57, pivotally secured on fixed pivot shafts 58, and having gear segment portions 59. As illustrated in FIG. 3, the gear segments 59 mesh with a double-sided rack 60 having teeth on the oposite faces thereof.

The double-sided rack 60 is disposed at the upper end of a metallic coupling member 61, having threadedly secured thereto, adjacent the lower end 62 thereof, the insulating operating rod 17. An annular spring plate 62a is fixedly supported by a plurality of tie-rods 63 from the lower side 64 of the pressurized tank 18. An opening accelerating compression spring 65 has its lower end seated upon the spring plate 62a. The upper end of the accelerating spring 65 is seated upon a cup-shaped spring seat 66, which is threadedly secured, as at 67, to the lower extremity 62 of the coupling member 61.

To provide a seal through an opening 68 of the tank 18, a metallic bellows 69 is provided. The lower end of the metallic bellows 69 is secured, as by suitable metal joining, to a ring 70 secured to the lower end of a tubular guide support 71, afiixed by bolts 72 to the lower side 64 of the metallic housing 18. The upper end of the metallic bellows is secured, as by soldering, to the coupling member 61.

From an inspection of FIG. 3 of the drawings, it will be apparent that upward opening motion of the insulating operating rod 17, as effected by the biasing action exerted by the opening accelerating spring 65, causes upward movement of the movable spring seat 66, and consequent upward movement of the coupling 61 and double-sided gear rack 60. Because of the meshing of the teeth associated with the double-sided rack 60 with the gear segments 59, the crank-arms 57 will be rotated about their pivot axes 58 in a direction away from each other, causing thereby the driving rollers 56 to move outwardly toward the outer ends of the channel member 54.

The outward movement of the driving rollers 56 will cause consequent downward opening movement of the cross-head structure 49, carrying with it the two movable pressure-generating contacts 52 and the two movable interrupting contacts 34. This will establish two pressuregenerating arcs 73 and two interrupting arcs 39, asmore clearly indicated in FIG. 4 of the drawings. It will be observed that the pressure-generating arcs 73 are estab: lished between the contact tips 75 and the relatively stationary pressure-generating contact fingers 76. During the existence of relatively high-amperage currents, the upper ends of the pressure-generating are 73 may transfer to a surrounding end metallic shell member 77 in a manner more fully brought out and described in United States patent application filed August 27, 1959, Serial No. 836,405, now US. Patent 3,110,791, issued November 12, 1963, to Wayne S. Aspey and Benjamin P. Baker, and assigned to the assignee of the instant application.

As illustrated in FIG. 3 of the drawings, the electrical circuit passing through the arc-extinguishing unit 13 generally comprises terminal stud 30, relatively stationary contact structure 32, left-hand movable interrupting contact 34, connecting portion 78, movable pressure-generating contact 52, relatively stationary pressure-generating contact 76, conducting support plate 79, relatively stationary pressure-generating contact 76, movable pressuregenerating contact 52, connecting portion 78, right-hand movable interrupting contact 34, right-hand relatively stationary contact structure 32 and to the right-hand terminal stud 30. l

During the opening operation the movable interrupting contacts 34 are moved downwardly within guide and fluid directing structures 80, generally comprising a tubular guide 81 having a lower portion 82, which extends through an opening 83 provided in the lower wall 84 of the insulate ing interrupting tube 40. In addition, an annular split clamping ring 85 encompasses the lower portion 82 of the guide tube 81. Surrounding the tubular guide 81 is a sleeve 86 of an arc-resistive material, such as polytetrafluoroethylene.

It will be noted that the upper end of the tubular guide member 81 has a plurality of jet apertures 87 provided therein. These jet apertures 87 register with openings 88 provided in a sleeve 89, also formed of polytetrafluoroethylene. The lower end of the sleeve 89 abuts a guide and sealing ring 90 also formed of polytetrafluoroethylene. Disposed within an orifice opening 91, provided at the upper side of the interrupter tube 40, is an orifice member 92, also formed of polytetrafluoroethylene. Partially surrounding the external side 93 of the interrupter tube 40 is a shield 94 formed of polytetra'fluoroethylene. In addition, disposed within the cylindrical supports 25 (FIG. 4) are shields 96, formed of polytetrafluoroethylene to protect the metallic supports 25 from the action of the interrupting are 39.

During the opening operation, as previously explained, the two movable contact structures 97, comprising the interrupting contacts 34, 52 and the interconnecting conducting portions 78, move downwardly, as a unit, to simultaneously establish a pair of pressure-generating arcs 73 and a pair of interrupting arcs 39. The two pressuregenerating arcs 73 set up an extremely high pressure within the region 46 within the interrupting tube 40.. The fluid, under pressure within the region 46, is ejected through the registered openings 87, 88 and through the orifice opening 99 to the region 100 externally of the tube 40 and adjacent the relatively stationary contact structures 32, as illustrated by the arrows 101 in FIG. 3. Arc-extinguishing action quickly follows, and the U-shaped movable contact structures 97 move downwardly to an open circuit position, such as illustrated in FIG. 4 of the drawings.

From the foregoing description of the invention it will be apparent that there is illustrated a novel interrupting structure 13 particularly suitable for the use of the liquefied gases, such as set forth in the United States patent application filed September 13, 1957, Serial No. 683,760, now US. Patent 3,150,245, issued September 22, 1964, to Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application.

Although the interrupting structure 13 has particular advantage when used with a liquefied gas, it is to be noted that a certain degree of interrupting effectiveness is also available by using the same interrupting structures with a suitable ordinary arc-extinguishing fluid, such as liquid, for example circuit-breaker oil.

From the foregoing description of the present invention, it will be apparent that there are disclosed novel types of circuit interrupters utilizing liquefied gas or the gas injected into the arcing zone. Although liquefied SF has been used as an example of :a possible liquefied gas, in describing the structure, it is to be clearly understood that liquefied selenium hexafiuoride, or any one or a mixture of two or more of liquefied gases enumerated below may be employed in substitution of liquid SP The gases which are suitable for use in interrupters of the type considered, have similar properties and characteristics as set out in the following table.

Vapor Dielectric Boiling Pressure, Strength Point, #/sq. in. Compared O. Gauge at With Air C. or N2 Although the foregoing liquefied gases may be used to advantage, exceptional and unusual performance is obtained with liquefied SP and liquefied SeF since the gaseous phases of these two materials are so highly effective in arc interruption and high dielectric insulation.

Disposed at the upper end of the side support plates 102 is a pair of bumpers 103, provided by an overlying channel member 104, biased upwardly by compression springs 105. Thus, upon downward retracting movement of the operating cross-head 49, the channel member 54 will strike the upper surfaces of the channels 104 and be resiliently brought to a cushioned stop.

FIG. 4 illustrates a modified type of arc-extinguishing unit, generally designated by the reference numeral 107. Many features of the modified unit 107 are similar to the unit 13 illustrated in FIG. 3 of the drawings; consequently, the same reference characters have been employed, Where possible.

In place of using an insulating interrupter tube 40, as was the case with the unit 13 of FIG. 3, a metallic interrupter tube 108 is employed. Aluminum has proved to be a very desirable metallic material to employ for the interrupter tube 108. Disposed within the interrupter tube 108, adjacent opposite ends thereof, are activated alumina filters 109, which purify the gas following its interrupting function. The U-shaped movable bridging contact structures 97 are substantially the same as before. However, it will be observed that insulating grommet seals 110 formed of polytetrafluoroethylene are employed. The interrupting orifices 112 are of simplified construction, and are also preferably formed of polytetrafluoroethylene. The operating linkage is substantially the same as described heretofore in connection with FIG. 3 of the drawings; consequently, a further description thereof appears unnecessary. By'utilizing an aluminum pressure tube 108, the interrupter 107 is less complicated and less expensive. In addition, the metal is particularly suitable for its pressure-resistant function. As shown, there are provided two polytetrafluoroethylene interrupter orifices 112 and four polytetrafluoroethylene grommet seals 110. A sheet of polytetrafluoroethylene 111 is provided to protect the lower wall of the aluminum pressure tube 108 from the effects of arcing. In addition, a sheet 113 is provided on top of the aluminum tube 108 to prevent the arcs from striking the top of the aluminum tube.

The moving contact system, as before, consists of two U -shaped members insulated from each other and mounted upon a race-track device. The contact operating means comprises a pair of levers, each with a gear segment, and both are driven by a common rack 60, which, in turn, is driven by the upstanding insulating operating rod 17 extending to ground potential. The outer ends of the two levers 57, as before, are provided with rollers 56, which engage the race-tracks 55 to drive the movable contacts 34, 52 in a vertical motion. The tracks 55 thus move up and down but are not restrained intheir lateral motion to allow self-alignment with the interrupter and accessibility for maintenance and inspection. By having the interrupter tube 108 formed of metal, there is assurance that the interrupter tube is at the same floating potential as is the casing 18 in the fully open-circuit position of the interrupter-107.

By the particular mechanism construction illustrated, it will be observed that toward the end of the closing operation, the force exerted upwardly on the race-tracks 55 by the rollers 56 is increased due to the angular position of the operating cranks 57. In other words, the torque exerted against the driving motion of the doublesided gear rack 60 results due to a shorter lever arm distance in a higher force being imposed upon the crosshead structure 49 at the end of the closing stroke, as illustrated in FIG. 3 of the drawings.

From the foregoing description, it will be apparent that there are provided considerable improvements over the interrupting construction set forth in the aforesaid patent application Serial No. 836,405.

The metallic pressure-resistant interrupter housing 114 of the modified arc-interrupting unit 107 has associated therewith, as shown, a pair of communicating passages 115, 116, which lead to a liquid-level measuring device, not shown, such as of the type set forth in United States patent application filed December 7, 1960, Serial No. 74,387 now US. Patent 3,099,724, issued July 30, 1963, to Sheldon D. Silliman and Bernard R. Johnson, and assigned to the assignee of the instant application. Briefly, such a liquid-level measuring device indicates the particular location of the liquid level 117 of the liquefied gas disposed within the housing 114, and is operable to set up an alarm circuit should the level 117 drop too low, due to a tank leak and consequently render the extinguishing unit 107 ineffective to accomplish its desired in terrupting task.

A distinct advantage of the crank-arm mechanism 118 of the present invention, together with the lower coupling 56 between the free ends of the crank-arms 57 and the race-ways 55 of the channel-shaped cross-head member 54 is that there is consequently omitted any lateral force exerted upon the movable contact assemblage. This is a distinct advantage since, if there were such lateral biasing force, there might result jamming of the movable contact rods 34, 52 through the several bushings 119 and 110. As a result, the entire movable contact assemblage is moved to its open and closed-circuit positions by forces having components only in the vertical direction, and not accompanied by laterally-directed rforces. Straight-line contact movement is the result with no binding forces being encountered during such movement.

The particular crank-arm mechanism 118 in addition also insures simultaneous movement of the two crankarms 57 so that they will be operated in unison.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

What is claimed is:

1. The combination in a live-tank fluid-blast type of circuit interrupter including a metallic pressure-resistant arc-extinguishing housing, a hollow insulating column for supporting said metallic pressure-resistant arc-extinguishing housing up in the air and adequate distance above ground potential, a pair of terminal bushings extending into said housing and carrying a pair of relatively stationary contacts at the interior ends thereof, a pressureresistant metallic interrupting chamber disposed interiorly within said housing and electrically connected to the outer metallic housing, said pair of relatively stationary contacts being situated adjacent one side of said pressureresistant metallic interrupting chamber, a pair of relatively stationary pressure-generating contacts disposed within said metallic interrupting chamber and electrically connected thereto, a pair of spaced-apart movable U-shaped contact structures, each movable U-shaped contact structure including a movable interrupting contact and a movable pressure-generatingcontact, the movable interrupting contact being cooperable with one of said firstmentioned relatively stationary contacts and the movable pressure-generating contact being cooperable with one of said relatively stationary pressure-generating contacts, a movable cross-head for carrying the pair of movable U-shaped contact structures, operating mecahnism for driving the cross-head comprising a pair of spaced-apart driving cranks having driving rollers adjacent the free ends thereof, means defining a race-way secured to and movable with said cross-head for accommodating the two driving rollers, a double-sided driving rack movable during the opening and closing operations of the circuit breaker for simultaneously driving said driving cranks in opposite directions of rotation at substantially the same speed, and an insulating operating rod extending upwardly interiorly of said insulating column and having said double-sided driving rack secured thereto adjacent the upper end thereof, whereby the capacitance efiects of the terminal bushings and the electrical connection between the inner metallic interrupting chamber and the outer metallic housing will assist in voltage division among the breaks during the opening operation.

2. A fluid-blast type of circuit interrupter including a metallic arc-extinguishing housing having a pair of terminal bushings extending therewithin, a metallic pressure-resistant interrupting chamber disposed within said housing and electrically connected thereto, a pair of spaced-apart relatively stationary contact structures sup ported by said pair of terminal bushings and situated adjacent one side of said metallic pressure-resistant interrupter chamber, a pair of relatively stationary pressuregenerating contacts disposed within said metallic interrupting chamber and secured adjacent one interior wall thereof and electrically connected thereto, a pair of spaced-apart movable U-shaped contact structures, each movable U-shaped contact structure including a movable interrupting contact and a movable pressure-generating contact, the movable interrupting contact being cooperable with one of said first-mentioned relatively stationary con- 8 tact structures and the movable pressure-generating contact being cooperable with one of said relatively stationary pressure-generating contacts, an insulating orifice structure to shield the passage of each movable interrupting contact from the metallic interrupting chamber from said one side thereof, whereby the establishment of two serially related pressure-generating arcs interiorly of said metallic pressure-resistant interrupting chamber generates pressure therein to effect the extinction of the two serially related interrupting arcs drawn between the relatively stationary and the movable interrupting contacts, and whereby the capacitance eifects of the terminal bushings and the electrical connection between the inner metallic interrupting chamber and the outer metallic housing will assist in voltage division among the breaks during the opening operation. 7

3. The combination in a live-tank fluid-blast type of circuit interrupter including a metallic pressure-resistant outer arc-extinguishing housing, a pair of terminal bushings extending into said metallic pressure-resistant housing and carrying a pair of relatively stationary contacts at the interior ends thereof, a metallic pressure-resistant internally-located interrupting chamber disposedwithin said outer housing and spaced from said relatively stationary contacts, said metallic interrupting chamber being electrically connected to the outer metallic housing, a pair of relatively stationary pressure-generating contacts secured adjacent an inner wall of said metallic inner interrupting chamber and electrically connected thereto, a pair of spaced-apart U-shaped movable contact structures movable through four insulated openings along the opposite side wall of said inner metallic interrupting chamber for establishing a pair of interiorly-disposed pressure-generating arcs and a pair of serially-related interrupting arcs, and a stationary insulating orifice structure for each movable contact structure secured adjacent the pair of pressure-generating contacts, whereby the capacitance effects of the terminal bushings and the electrical connection between the inner metallic interrupting chamber and the outer metallic housing will assist in voltage division among the breaks during the opening operation.

4. A fluid-blast type of circuit interrupter including a metallic arc-extinguishing housing having a pair of terminal bushings extending therewithin, a pressure-resistant metallic interrupting chamber disposed within said housing and electrically connected thereto, a pair of spaced-apart relatively stationary contact structures supported by said pair of terminal bushings and situated adjacent one side of said pressure-resistant metallic interrupting chamber, a pair of insulating orifice openings provided in said one side of said metallic pressure-resistant interrupting chamber, a pair of relatively stationary pressure-generating contacts disposed interiorly of said metallic interrupting chamber and secured to an inner wall thereof and electrically connected thereto, a pair of spaced-apart movable U-shaped contact structures movable into the opposite side of said metallic interrupting chamber through insulated openings, each movable U-shaped contact structure including a movable interrupting contact and a movable pressure-generating contact, the movable interrupting contact of each movable U-shaped contact structure being movable through the insulating orifice opening and into engagement with one of said relatively stationary contact structures, and the associated movable pressure-generating contact of each U-. shaped movable contact structure being cooperable with one of said interiorly-located relatively stationary pressure-generating contacts for generating pressure within the metallic pressure-resistant interrupting chamber to create an arc-extinguishing flow through the orifice openings, whereby the capacitance efiects of the terminal bushings and the electrical connection between the inner metallic interrupting chamber and the outer metallic 9 10 housing will assist in voltage division among the breaks 3,110,791 11/63 Aspey et a1 200145 during the opening operation. FOREIGN PATENTS References Cited by the Examiner 1331166- ermany. UNITED STATES PATENTS 5 5,400 1826 Great Britain. 1,824,903 9/31 Kuhn 200-150 394,741 7/33 Great Britain, 2,138,191 11/38 Noyes 200-151 2,252,983 8/41 Rossman 200150 KATHLEEN H. CLAFFY, Primary Examiner. 2292547 8/42 Sadler 10 MAX L. LEVY, ROBERT K. SCHAEFER, BERNARD A ExanTl-ners 2,933,576 4/60 Friedrich et a1. 200150 3,052,783 9/62 Buron 200148 

1. THE COMBINATION IN A LIVE-TANK FLUID-BLAST TYPE OF CIRCUIT INTERRUPTER INCLUDING A METALLIC PRESSURE-RESISTANT ARC-EXTINGUISHING HOUSING, A HOLLOW INSULATING COLUMN FOR SUPPORTING SAID METALLIC PRESSURE-RESISTANT ARC-EXTINGUISHING HOUSING UP ON THE AIR AND ADEQUATE DISTANCE ABOVE GROUND POTENTIAL, A PAIR OF TERMINAL BUSHINGS EXTENDING INTO SAID HOUSING AND CARRYING A PAIR OF RELATIVELY STATIONARY CONTACTS AT THE INTERIOR ENDS THEREOF, A PRESSURE RESISTANT METALLIC INTERRUPTING CHAMBER DISPOSED INTERIORLY WITHIN SAID HOUSING AND ELECTRICALLY CONNECTED TO THE OUTER METALLIC HOUSING, SAID PAIR OF RELATIVELY STATIONARY CONTACTS BEING SITUATED ADJACENT ONE SIDE OF SAID PRESSURERESISTANT METALLIC INTERRUPTING CHAMBER, A PAIR OF RELATIVELY STATIONARY PRESSURE-GENERATING CONTACTS DISPOSED WITHIN SAID METALLIC INTERRUPTING CHAMBER AND ELECTRICALLY CONNECTED THERETO, A PAIR OF SPACED-APART MOVABLE U-SHAPED CONTACT STRUCTURES, EACH MOVABLE U-SHAPED CONTACT STRUCTURE INCLUDING A MOVABLE INTERRUPTING CONTACT AND A MOVABLE PRESSURE-GENERATING CONTACT, THE MOVABLE INTERRUPTING CONTACT BEING COOPERABLE WITH ONE OF SAID FIRSTMENTIONED RELATIVELY STATIONARY CONTACTS AND THE MOVABLE PRESSURE-GENERATING CONTACT BEING COOPERABLE WITH THE OF SAID RELATIVELY CONTACT BEING COOPERABLE WITH ONE A MOVABLE CROSS-HEAD FOR CARRYING THE PAIR OF MOVABLE U-SHAPED CONTACT STRUCTURES, OPERATING MECHANISM FOR DRIVING THE CROSS-HEAD COMPRISING A PAIR OF SPACED-APART DRIVING CRANKS HAVING DRIVING ROLLERS ADJACENT THE FREE ENDS THEREOF, MEANS DEFINING A RACE-WAY SECURED TO AND MOVABLE WITH SAID CROSS-HEAD FOR ACCOMMODATING THE TWO DRIVING ROLLERS, A DOUBLE-SIDED DRIVING RACK MOVABLE DURING THE OPENING AND CLOSING OPERATIONS OF THE CIRCUIT BREAKER FOR SIMULTANEOUSLY DRIVING SAID DRIVING CRANKS IN OPPOSITE DIRECTIONS OF ROTATION AT SUBSTANTIALLY THE SAME SPEED, AND AN INSULATING OPERATING ROD EXTENDING UPWARDLY INTERIORLY OF SAID INSULATING COLUMN AND HAVING SAID DOUBLE-SIDE DRIVING RACK SECURED THERETO ADJACENT THE UPPER END THEREOF, WHEREBY THE CAPACITANCE EFFECTS OF THE TERMINAL BUSHINGS AND THE ELECTRICAL CONNECTION BETWEEN THE INNER METALLIC INTERRUPTING CHAMBER AND THE OUTER METALLIC HOUSING WILL ASSIST IN VOLTAGE DIVISION AMONG THE BREAKS DURING THE OPENING OPERATION. 